# Interpretation of Bi-207 decay spectrum

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## Summary:

Please help me interpret the Bi-207 decay spectrum, e.g. origin of the peaks, whether beta particles or gammas.
I measured the decay spectrum of Bi-207 as a beta source with scintillation detector and now I am trying to interpret the information given by the spectrum. As far as I know, the Bi-207 nuclei decay to the excited states of Pb-207 primarily via EC and a small beta+ branch, emitting beta particles of E_max=806keV, E_ave=383 keV, and the excited states of Pb-207 decays via IC, emitting conversion electrons of ~ 1 MeV. In addition, the Bi-207 decay was accompanied by emission of gamma rays of 570 keV (98%), 1064 keV(74.6%), and 1770 keV (6.87%).

In this measurement Bi-207 was used as the beta source to test the detector response to beta particles, however, in similar measured spectrum of Bi-207 made by others, it was described as the gamma spectrum with peaks at 570 and 1064 keV.

Now I am quite confused of the measured spectrum, e.g. the origin of the two peaks, and what else information can be drawn from the spectrum.
Any helps would be very appreciated. Thank you in advance!

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bobob
Gold Member
Gammas from the decay of the 207Pb excited states. Look up the level schemes.

gleem
I am assuming the abscissa for your spectrum is channel number is that correct? If so what are the energies that the peaks represent? I also assume that at some point you calibrated the detector.

gleem
I would have expected to see a few sharper peaks also.

Gammas from the decay of the 207Pb excited states. Look up the level schemes.
Thanks, now I have figured it out. Those "peaks" were the Compton edges of the Pb-207 gammas.

I am assuming the abscissa for your spectrum is channel number is that correct? If so what are the energies that the peaks represent? I also assume that at some point you calibrated the detector.
Yes, they were the Compton edges of gammas. Thanks.

gleem